The present invention relates to treatment of tissue by ultrasound and, more particularly, to apparatus for delivering ultrasound.
U.S. Pat. No. 6,379,320 discloses a probe for coagulating tissue by therapeutic ultrasound delivered from a planar transducer. Other ultrasound delivery apparatuses are disclosed in U.S. Pat. No. 5,630,837 which uses at least one annular piezoelectric element or U.S. Pat. No. 5,762,066 in which the piezoelectric elements are arranged in two chambers.
Focused transducers for bringing about high-temperature heating (the “HIFU” technique) are disclosed in the following French patent applications: 2,673,542, 2,700,878; 2,717,942; 2,750,340; 2,778,573; 2,778,574; 2,794,018; 2,807,827; 2,679,125; 2,715,822.
It has also been proposed to use cylindrical transducers in probes—in particular urethral probes—for producing radial emission, U.S. Pat. No. 5,391,197 states that the piezoelectric elements are cylindrical and focusing, U.S. Pat. No. 5,522,869 discloses tissue temperature measurement, U.S. Pat. No. 5,549,638 employs cylindrical piezoelectric elements and measures temperature in the tissue, U.S. Pat. No. 5,620,479 discloses tubular piezoelectric elements, U.S. Pat. No. 5,733,315 states that the piezoelectric elements are arranged around a central tube some of them being deactivated to avoid heating of the rectum. U.S. Pat. No. 5,895,356 states that the piezoelectric elements are circular and focusing. These various apparatuses have the disadvantage of the ultrasound field being diverging which can be harmful to the depth effectiveness of treatment.
Therapy transducers associated with imaging for guiding purposes are also proposed. U.S. Pat. No. 5,697,897 discloses an endoscope provided with a therapeutic ultrasound source. U.S. Pat. No. 5,471,988 discloses various endoscope configurations provided with a therapy transducer. However, in each case this transducer is focusing. The transducer is associated with an imaging transducer or optical system. U.S. Pat. No. 6,050,943 discloses piezoelectric elements having three functions: imaging, therapy and temperature control.
Vibrating instruments are also known, these comprising a transducer coupled to a tool via an ultrasound conductor. The tool can be a knife or pincer-like instrument for cutting or coagulating tissue. Coagulation results from the temperature rise of the tissue in contact with the tool, by friction. Coagulation depth depends on tissue thermal conduction and is consequently low. An instrument known as the “Harmonic scalpel” which is activated by ultrasound is marketed by the HS company, Ethicon Endo-surgery, Cincinatti, Ohio, US.
Various medical instruments employ radiofrequencies. Radiofrequency coagulators employ alternating current. An alternating current is caused to pass through the tissue, which heats up by ohmic heating. A distinction is made between bipolar coagulators (the effect is in the area between two electrodes) and monopolar coagulators (heating occurs in the immediate surroundings of the tip, the current return path being via a ground plate in contact with the patient). Endoscopic scalpels all are provided with a loop that is activated by a current and which cuts or coagulates the tissue depending on the current used. Recently, bipolar loops have appeared. Numerous other apparatuses, identified below by their commercial name, used radio frequencies:                Coagulating Intermediate Cutting (CIC, CoCut BMP) uses an HF electrode and proposes chopping coagulation and cutting periods.        Ligasure: a bipolar pincer apparatus for vessel sealing (ESVS Valleylab Boulder Colo. US). In urology this is of value for reducing time and amount of blood lost by the patient.        
Laser coagulators have also been proposed using different types of laser for coagulating veins or small blood vessels.
Various applications of ultrasound to treatment are discussed in the following Articles:
Author(s)TitleJournalLAFON C; CHOSSON S;The feasibility of constructingUltrasonics,PRAT F; THEILLERE Y;a cylindrical array with a plane37(9): 615-21 2000CHAPELON JY; BIRER A;rotating beam for interstitialMayCATHIGNOL Dultrasound applicationLAFON C. CHAVRIER F.Theoretical comparison of twoMed Biol EngPRAT F. CHAPELON JY.interstitial ultrasound applicatorsComput, 1999,CATHIGNOL D.designed to induce cylindrical37: 298-303zones of tissue ablationLAFON C. PRAT F.In vivo effects of interstitialIEEE, 1998,CHAPELON JY. GORRY F.ultrasound plane applicator on2: 1423-1426MARGONARI J.Dunning tumorsTHEILLERE Y.CATHIGNOL D.LAFON C. PRAT F.Cylindrical thermal coagulationCHAPELON JY. GORRY F.necrosis using an interstitialMARGONARI J.applicator with a plane ultrasonicTHEILLERE Y.transducer: in vitroCATHIGNOL D.and in vivo experiments versuscomputer simulationLAFON C. CHAPELON JY.Design and in vitro results of aUltrasonics, 1998,PRAT F. GORRY F.high intensity ultrasound interstitial36: 683-687THEILLIERE Y.applicatorCATHIGNOL D.LAFON C. CHAPELON JY.Design and preliminary resultsUltrasound inPRAT F. GORRY F.of an ultrasound applicator formedicine & biology,MARGONARI J.interstitial thermal coagulationvol. 24, no1,THEILLIERE Y.113-122, 1998CATHIGNOL D.LAFON C. THEILLERE Y.Ultrasound interstitial applicatorIEEE, 1999,PRAT F. AREFIEV A.for digestive endoscopy:2: 1447-1450CHAPELON JY.in vivo destruction of bilaryCATHIGNOL D.tissuesLAFON C. THEILLERE Y.Development of an interstitialUltrasound inPRAT F. AREFIEV A.ultrasound applicator for endoscopicmedicine & biology,CHAPELON JY.procedures: animalvol. 26, no4,experimentation669-675, 2000LAFON C; CHAPELON JY;Design and preliminary resultsUltrasound MedPRAT F; GORRY F;of an ultrasound applicator forBiol, 24(1): 113-22MARGONARI J;interstitial thermal coagulation.1998 JanTHEILLERE Y;CATHIGNOL DPRAT F. LAFON C.A high-intensity US probe designedGastrointestinalMARGONARI J. GORRY F.for intraductal tumorendoscopy, 1999,THEILLERE Y.destruction: experimental results.50(3): 388-392CHAPELON JY.CATHIGNOL D.PRAT F. LAFON C.Destruction of a bile duct carcinomaGastrointestinalTHEILLERE Y. FRITSCH J.by intraductal highendoscopy, 2001CHOURY AD. LORAND I.intensity ultrasound duringJun, 53(7): 797-800CATHIGNOL D.ERCP.LAFON C.; MELO DEOptimizing the shape of ultrasoundMed. Phys. 29 (3),LIMA D.; THEILLERE Y.;sound transducers for interstitialMarch 2002.PRAT F. CHAPELON JY;thermal ablationCATHIGNOL D.
Known devices raised certain problems which are not necessarily identified in the state-of-the-art.
Limit Risks of Hemorrhage
The surgeon is always faced with the problem of hemostasis. He should coagulate the vessels during surgery and ensure they will remain sealed after intervention. Arterial bleeding is frequently easy to identify as blood flows is pulsed. Veins are problematic because they can be difficult to seal. The danger of bleeding is particularly serious in endoscopic surgery because it is more difficult to master.
Reduce Risk of Glycine Resorption
Endoscopic surgery is frequently performed in aqueous medium: saline solution or glycine; glycine is a liquid used during endoscopic surgery; it is an electrical insulator. When pressure increases, glycine can be resorbed by the patient's venal system which can lead to the so-called TURP syndrome. This is a reason why, during endoscopic surgery (of the prostate, endometer) the amount of electrolyte in the blood is monitored and duration of treatment is limited. For these reasons also, it is important to successfully coagulate the veins.
Limit Risk of Recurrence
During cancer surgery, the insertion of a surgical instrument introduces a risk of spreading tumor cells in the organism. In bladder cancer for example, it is suspected that the simple fact of touching the tumor can increase the risk of recurrence. It would consequently be useful to coagulate tissue remotely without touching it.
Be Selective
Conventional instruments have the same effect whether the tissue is normal or tumor. One consequently looks for an instrument which could selectively destroy certain tissue, for example tumor tissue.